Field of the Invention
The invention relates to a gas turbine and steam turbine installation with a waste-heat steam generator connected downstream of a gas turbine. The heating surfaces of the waste-heat steam generator are connected into the water/steam cycle of a steam turbine. A gasification device for gasifying fuel is connected, with a fuel line, upstream of a combustion chamber of the gas turbine. A saturator is connected into the fuel line. The gasified fuel is guided in counterflow to a water flow which is guided in a saturator cycle.
A gas turbine and steam turbine installation with integrated gasification of fossil fuel usually includes a fuel gasification device which is connected, at the outlet end, to the combustion chamber of the gas turbine via a number of components provided for gas cleaning. The waste-heat steam generator can then be connected downstream of the gas turbine, at a flue gas side. The heating surfaces of the waste-heat steam generator are connected into the water/steam cycle of the steam turbine. Such an installation is known, for example, from Published UK Patent Application GB-A 2 234 984.
In order to reduce the pollutant emission during the combustion of the gasified fossil fuel, a saturator is connected, in this installation, into the fuel line between the gasification device and the combustion chamber of the gas turbine. The gasified fuel is loaded with water vapor in the saturator. For this purpose, the gasified fuel flows through the saturator in counterflow to a flow of water which is guided within a water cycle. This water cycle is designated as saturator cycle. In order to set a temperature level in the saturator which is sufficient for loading the gasified fuel with water vapor, heat is coupled into the saturator cycle by cooling the tapped or extracted air and/or by cooling the crude gas from the fuel gasification.
In this installation, however, the operation of the saturator depends on the operating condition of the gasification device and/or on the operating condition of an air separation unit connected upstream of the gasification device, so that this concept only has limited flexibility. With respect to control, furthermore, such a concept is comparatively complicated and therefore susceptible to failure.
U.S. Pat. No. 5,319,924 discloses to preheat, in a heat exchanger, the feed water to be fed into a saturator, wherein it is possible to provide the heat exchanger with uncleaned crude gas on the primary side. In addition, a saturator configured as a fuel humidifier is known from Published, Non-Prosecuted Patent Application DE 43 21 081 in which a heat exchanger, which is supplied with feed water on the primary side, is provided for preheating the saturator water.
In the article "Effiziente und umweltfreundliche Stromerzeugung im GUD-Kraftwerk mit integrierter Vergasung" [Efficient and environmentally friendly power production in a gas and steam power plant with integrated gasification] by G. Haupt in "Elektrotechnik und Informationstechnik" [Electrical engineering and information technology], AT, Springer Verlag, Vienna, Volume 113, No. 1,2 (Feb. 1996), pages 102-105, the heating in a heat exchanger of a water flow which is to be fed into a saturator is described. The water flow is heated in a heat exchange with feed water extracted from the water/steam cycle of the steam turbine and supplied in a dedicated reservoir ("flash tank") connected into a circulating circuit. A heat exchanger is connected into this circulating circuit and in the heat exchanger the feed water absorbs heat from a partial flow of compressed air, the air being appropriately cooled in the process.